Light modulating engine

ABSTRACT

The invention relates to a light illumination apparatus comprising at least one exposure head ( 12 ) and at least two light modulating arrangements ( 20 ), each of said two light modulating arrangements ( 20 ) comprising a spatial light modulator ( 31, 32 ) and an associated light emitter arranged for illumination of an illumination surface ( 15 ) via said spatial light modulator ( 31, 32 ), each of said two light modulating arrangements ( 20 ) being digitally controlled, said apparatus comprising means for performing a relative movement between said at least one exposure head and said illumination surface ( 15 ) in at least one direction (x;y).

FIELD OF THE INVENTION

The present invention relates to a light illumination apparatusaccording to claim 1.

BACKGROUND OF THE INVENTION

A typical light illumination apparatus comprises an arrangement adaptedfor illuminating a light sensitive material. Such material may e.g.comprise printing plates, materials adapted for rapid prototyping, film,etc. The illuminating is performed for the purpose of obtaining certainchanges of properties of the illuminated material. Such illumination maythus e.g. result in the establishment of an image on the illuminatedmaterial or a certain structure.

In order to obtain the desired illumination, light must be modulated.One prior art method of modulating light transmitting to an illuminationsurface is to apply a single or multiple beam laser, which may bemodulated when performing a scanning movement over the illuminationsurface.

Another and more recent way of illuminating an illumination surface isto apply a so-called spatial light modulator. Examples of suchmodulators may be a DMD, an LCD, etc. The spatial light modulator isadapted for modulating an incoming light beam into a number ofindividually modulated light beams.

A problem of the prior art is that the obtainable modulating speed issomewhat limited due to the nature of the applied light modulatorscombined with the required energy and illumination speed for someapplications.

SUMMARY OF THE INVENTION

The invention relates to a light illumination apparatus comprising atleast one exposure head and at least two light modulating arrangements,each of said two light modulating arrangements comprising a spatiallight modulator and an associated light emitter arranged forillumination of an illumination surface via said spatial lightmodulator,

-   each of said two light modulating arrangements being digitally    controlled,-   said apparatus comprising means for performing a relative movement    between said at least one exposure head and said illumination    surface in at least one direction.

According to the invention it has been realized that a movable exposurehead may advantageously comprise two spatial light modulators, therebyfacilitating a scanning by means of a two modulators at one time.

In an embodiment of the invention, the light illumination apparatuscomprises at least one exposure head and at least two light modulatingarrangements

-   each of said two light modulating arrangements comprising a spatial    light modulator and an associated light emitter arranged for    illumination of an illumination surface via said spatial light    modulator,-   each of said two light modulating arrangements being digitally    controlled,-   said apparatus comprising means for performing a relative movement    between said at least one exposure head and said illumination    surface in at least one direction.

In an embodiment of the invention, said at least two light modulatingarrangements are arranged on the same exposure head.

In an embodiment of the invention, said relative movement is a scanningmovement.

In an embodiment of the invention, said relative movement is establishedby moving the at least one exposure head relative to said illuminationsurface.

In an embodiment of the invention, said relative movement is establishedby moving said illumination surface relative to the at least oneexposure head.

In an embodiment of the invention, at least one exposure head comprisestwo light modulating arrangements. It has thus been established that acost-effective way of illuminating an illumination surface is byapplying two spatial light modulation arrangements in one exposure head,thereby obtaining an illumination arrangement, which may illuminate theillumination surface in a relatively high-speed scanning movement. Inthis context is noted that an exposure head may be somewhat difficult todeal with when the weight of the moving arrangement increases.

In an embodiment of the invention, said relative movement is establishedby moving said illumination surface relative to the at least oneexposure head.

In an embodiment of the invention, at least one exposure head comprisestwo light modulating arrangements.

In an embodiment of the invention, said light modulating arrangementsare arranged on at least two different exposure heads and where saidexposure heads perform scanning movements over the illumination surface.When applying two or more free-running scanning exposure heads, theillumination may be optimized carefully to the illumination surface,thereby avoiding so-called “over-scanning”. In principle, anysuperfluous scanning may be avoided or at least minimized due to thefact that the scanning performed by the exposure heads may be adapted toavoid any conflicting movement between the applied exposure heads. Thus,a number of free-running exposure heads illuminating an illuminationsurface by scanning is quite advantageous with respect to efficiency dueto the fact that the scanning movement as such ensures a high-speedillumination, while the free-running heads ensure that the illuminationof the illumination area may be optimized as described above.

According to a further embodiment of the above-described free-runningexposure heads, the number may exceed two, e.g. three or further headsin total. Moreover, each head may e.g. comprise two or furtherillumination arrangements, e.g. of the type described in FIG. 2.

When said spatial light modulators being arranged so as to illuminatetwo substantially separate sub-areas of said illumination surface, anadvantageous embodiment of the invention has been obtained.

When said spatial light modulating arrangements being aligned so thatthe rows of both light modulators are parallelly oriented, anadvantageous embodiment of the invention has been obtained.

When said spatial light modulating arrangements being aligned so thatthe neighboring rows of the two spatial light modulators are positionedsubstantially so that the distance (DN) between the two neighboring rowsof the two spatial light modulators are substantially the same as thedistance (DR) between the rows of the individual light modulators, anadvantageous embodiment of the invention has been obtained.

When the “x-projection” (D1) of the distance between the centers of thetwo spatial light modulators being less than 200 millimeters, preferablyless than 150 millimeters, preferably substantially 120 millimeters, anadvantageous embodiment of the invention has been obtained.

When the “y-projection” (D2) of the distance between the centers of thetwo spatial light modulators being less than 50 millimeters, preferablyless than 35 millimeters, preferably substantially 25.6 millimeters or20.5 millimeters when applying SXGA, and XGA respectively, anadvantageous embodiment of the invention has been obtained.

When the distance between the centers of the two spatial lightmodulators being less than 121.73 millimeters (XGA) or 122,70millimeters (SXGA), an advantageous embodiment of the invention has beenobtained.

According to the invention it has been recognized that a very closepositioning of the light modulating arrangements facilitates an improvedoverall scanning speed in the sense that the effective scanning area isoptimized. A minimizing of the distance therefore results in that bothspatial light modulators of the exposure head are active as long aspossible at the ends of the scanning lines.

When said exposure head comprising cooling means, an advantageousembodiment of the invention has been obtained.

Cooling means may e.g. comprise electrically driven fans.

When each spatial light modulating arrangement comprising individualcooling means, an advantageous embodiment of the invention has beenobtained.

When said substantially separate sub-areas comprising neighboringsurfaces of said illumination surface, an advantageous embodiment of theinvention has been obtained.

When said at least one direction being substantially transverse to arelative movement of said illumination surface, an advantageousembodiment of the invention has been obtained.

When said at least one direction establishing that an illuminated pixelon said illumination surface is illuminated by means of a least twolight modulators of said spatial light modulator, an advantageousembodiment of the invention has been obtained.

When said at least one direction establishing that an illuminated pixelon said illumination surface is illuminated by means of at least onemodulator row of said spatial light modulator, an advantageousembodiment of the invention has been obtained.

When said exposure head being movable in at least two directions withrespect to said illumination surface, an advantageous embodiment of theinvention has been obtained.

When said light emitter comprising a light source, an advantageousembodiment of the invention has been obtained.

When said light emitter comprising at least on light emitting end of anoptical guide coupled to a light source, an advantageous embodiment ofthe invention has been obtained.

When said light emitter comprising a lamp, an advantageous embodiment ofthe invention has been obtained.

When said light emitter comprising a LED matrix, an advantageousembodiment of the invention has been obtained.

When said spatial light modulator comprising a DMD chip, an advantageousembodiment of the invention has been obtained.

The spatial light modulating array of the illumination arrangements maybe a transmissive micro-mechanical shutter array as disclosed in WO 9847048 and WO 98 47042, which are hereby included by reference.

Another type of spatial modulator may be a DMD modulator or e.g. LCDlight modulator.

When said spatial light modulator comprising a micro-mechanicaltransmissive light modulator, an advantageous embodiment of theinvention has been obtained.

When said illumination surface comprising a printing plate, anadvantageous embodiment of the invention has been obtained.

When said illumination surface comprising a light sensitive material,such as epoxy, an advantageous embodiment of the invention has beenobtained. Other light sensitive materials may be applied as well withinthe scope of the invention such as emulsions for silkscreen printing,PCB emulsions, etc.

According to the invention, the illumination arrangement may be appliedfor so-called rapid prototyping.

Moreover, the invention relates to a method of illuminating anillumination surface whereby at least two light modulating arrangementsarranged on at least one exposure head, each comprising a spatial lightmodulator illuminate the illumination surface by a scanning movement.

In an embodiment of the invention, said at least two light modulatingarrangements are arranged on the same exposure head.

In an embodiment of the invention, said at least two light modulatingarrangements are arranged on different free-running exposure heads.

In an embodiment of the invention, the illumination is performed bymeans of a light illumination apparatus according to any of the claims1–31.

THE FIGURES

The invention will be described in the following with reference to thedrawings where

FIG. 1 illustrates a view of an exposure system, according to anadvantageous embodiment of the invention,

FIG. 2 illustrates a cross-section of an illuminating arrangement,according an embodiment of the invention,

FIG. 3 a illustrates a scanning pattern of an exposure head with respectto an illumination surface and where

FIG. 3 b illustrates a further scanning pattern of an exposure head withrespect to an illumination surface

FIG. 4 a illustrates an advantageous positioning of the illuminatingarrangements on the exposure head and where

FIG. 4 b–4 c illustrate further embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 illustrates a view of a few main components of an exposuresystem, according to an advantageous embodiment of the invention.

The illustrated system comprises an exposure head 12 comprising twoillumination arrangements 20 arranged for illumination of anillumination surface 15. The exposure head 12 is suspended in asuspension (not shown). The suspension facilitates movement in thedirection of the arrows under control by suitable electronic circuits(not shown).

For illustrative purposes, two illumination areas I1, I2 illuminated bythe spatial light modulators (e.g. DMD chips) arranged in theillumination arrangements 20 are indicated on the illumination surface.The illumination areas I1 and I2, may e.g. comprise 1024×768 (XGA)pixels or 1280×1024 pixels (SXGA) if applying e.g. TI DMD-chips. Themodulated pixels will, if applying a scanning movement, be switcheddynamically from row to row (or column to column) thereby applyingseveral pixels (e.g. a complete row of a spatial light modulator) forillumination of a single pixel on the illumination surface. Thereby, thedelivered optical energy to a single pixel is increased.

According to the illustrated embodiment, the exposure head is moved inthe X-direction and the illumination surface 15 is moved stepwise in theY-direction.

Evidently, other relative movements may be applied within the scope ofthe invention. A further advantageous embodiment of the invention maye.g. imply a relative movement of the exposure head 12 in bothdirections X and Y while keeping the illumination surface stationary.

The spatial light modulating array of the illumination arrangements maybe a transmissive micro-mechanical shutter array as disclosed in WO 9847048 and WO 98 47042, which are hereby included by reference.

Another type of spatial modulator may be a DMD modulator.

FIG. 2 illustrates a preferred embodiment of one of the light modulatingarrangements 20 of FIG. 1. The first part 21 of the arrangement 20produces a focused and uniform beam of light. It comprises a lamp 210, alamp driver 211, a blower 216 and a fan 217, a protection glass 212, ashutter 213, a light-integrating rod 214 and beam shaping optics 215.

The type of lamp 210 depends on the type of plate to be exposed.Possible types comprise conventional short arc bulbs, laser sources,diode arrays and more. A preferred conventional lamp might have a powerconsumption of 270 W, but the present invention is not in any waylimited to this value, nor to the mentioned types of lamps. Alternativessuch as 250 W and 350 W may be considered.

The light from the lamp 210 is transmitted through a filter (e.g. IR orUV-filter depending on the application) 212, functioning as aninterference filter, and through a shutter mechanism 213, making itpossible to turn off the light beam without turning off the lamp. Thisis important as most lamp types need time before their light intensityand frequency is unvarying. A blower 216 and a fan 217 ensure thecooling of the lamp 210.

Subsequently the light beam is transmitted through a light-integratingrod 214. Thereby the light is mixed, making the light throughout thebeam uniform with regards to intensity. This ensures that the light inthe periphery of the beam has the same intensity as the light in thecenter of the beam. When the light leaves the light-integrating rod 214,the beam shaping optics 215 focuses it.

The next part of the arrangement 20 modulates the light beam to reflectelectronically stored image data. It comprises a light-modulating means22 and means 224 for directing the unmodulated light beam towards thelight-modulating means 22 without disturbing its modulated light beamoutput.

Suited light-modulating means 22 comprises DMD modulators, transmissiveshutters including LCD and micro-mechanical shutters and more. For thepreferred embodiment of FIG. 2, a DMD light-modulating chip 220 mountedon a PCB 221 with a cooling plate 222 and a temperature sensor 223 isused.

The light directing means 224 depends on the type of light-modulatingmeans 22 used. For transmissive light modulating means the unmodulatedlight beam is directed towards one side of the light modulating means,and the modulated light beam is emitted from the other side. In such anarrangement the light directing means 224 might be excluded.

For DMD modulators the unmodulated light beam is directed towards thesame point as where the modulated light beam is emitted. Thisnecessitates the use of light directing means 224. In the preferredembodiment of FIG. 2, a TIR-prism is used for light directing means. TIRis an abbreviation meaning ‘Total Internal Reflection’. A TIR-prismcomprises a surface 225 which will act as a mirror to light coming fromone direction (from the left for this specific embodiment), and will letlight coming from another direction (from the top for this specificembodiment) straight through.

The last part of the arrangement 20 focuses the multiple modulated lightbeams emitted from the light modulating means 220 on an illuminationsurface 24 (printing plate). It comprises a set of lenses/a macro lens230 located within a housing 23. FIG. 3 a illustrates a scanning patternof an exposure head with respect to an illumination.

The illustrated scanning pattern obtained by the light illuminationapparatus according to the invention, e.g. the illumination arrangementas described in FIG. 2, involves that two illuminating arrangements 31,32 of an exposure head 30 a perform a relative movement with respect toan illumination surface. Both illumination arrangements 31, 32 arearranged on the same exposure head 30 a.

One of the illustrated illumination arrangements 31 illuminates the subareas SUB1 and the other illumination arrangement 32 illuminates the subareas SUB2.

It should be noted that the exposure head 30 a illuminates theillumination surface by modulated light in both directions in a scanningmovement as indicated by the horizontal arrows while shifting betweeneach scanning movement in steps 301, as indicated by the vertical arrow.

The y-axis movement is here performed as steps corresponding to thetotal transverse scanning width obtained by both light illuminatingarrangements in combination.

FIG. 3 b illustrates a further scanning pattern of an exposure head 30 bwith respect to an illumination surface.

According to the illustrated embodiment of the invention, an exposurehead 30 b comprises two spatial light modulators 31, 32 (theillumination arrangements carrying the spatial modulators are notillustrated). The applied illumination arrangements 31, 32 may e.g. bothbe the illustrated illumination arrangement of FIG. 2. According to theillustrated embodiment, two spatial light modulators 31, 32 (or theresulting illuminated surface corresponding to I1, and I2 of FIG. 1) arearranged and displaced only in the Y-direction.

The exposure head 30 b is performing a scanning movement back and forthin the X-direction. Moreover, the illumination surface or the exposurehead performs a relative movement in the Y-direction involving basicallytwo different steps, a micro step 302 and a macro step 303.

According to the illustrated embodiment, eight sub-areas SUB1 and eightsub-areas SUB2 are illuminated by performing the micro-steps 302.Thereafter, a macro step 303 is performed and a new set of sub-areas,SUB1 and SUB2, is illuminated by performing further micro steps 302.

It should be emphasized that several other scanning methods (patterns)may be applied within the scope of the invention.

FIG. 4 a illustrates an advantageous positioning of the illuminatingarrangements (here=optical engines) on the exposure head of e.g. FIG. 3a. The illumination arrangement 20, which e.g. may be the oneillustrated in FIG. 2, is indicated by dashed lines.

The dimensions of the optical engine are very important for theproductivity and cost of the machine. The two illuminating arrangements20 of the exposure head are located so that the obtainable illuminatedareas are adjacent in the direction of the y-axis (not to be confusedwith the scanning and modulator axis). This implies that there is acenter distance between the optical engines in the x-axis, see FIG. 4 a.

The mutual distance between the engines in the x-axis implies that it isnecessary to expose longer than the actual plate length so that bothheads have passed the entire plate (the illumination surface). Thissuperfluous “over-scan” is twice the center distance D1. This over-scanreduces the productivity and increases the width of the x-movement andthus the width of the machine. The center distance must therefore be aslow as possible. An example of such minimized distance may e.g. beCenter distance, x-axis: D1=120 mmCenter distance, y-axis: D2=(XGA) 20.48±0.002 mm and D2(SXGA)=25.6±0.002 mm

The lower limit is defined by the optics and the further illuminationarrangement component, e.g. the macro lens 230 of FIG. 2. A fixture (notshown) will allow adjustment in the illumination plane, i.e. adjustmentin x- and y-axis, and rotation about the z-axis, of the optical enginesindividually. This implies that the image must be accurately parallel tothe flange of the macro lens house, so that both images will be in thesame plane. The flange on the house is used to mount the house to thefixture, in the z-direction. The bottom side of the flange will definethe focus, so that the optical engines can be mounted against a flatsurface, and thus having focus in the same plane.

FIG. 4 b illustrates a further embodiment of the invention, where theapparatus comprises four light modulating arrangements 53, 54, 55, 56,e.g. of the type illustrated in FIG. 2, arranged on an exposure head 50.

The four light modulating arrangements 53, 54, 55 and 56 all movetogether due to the fixation to the same exposure head. A scanning mayadvantageously be performed in several different ways, e.g. according tothe principles illustrated in FIG. 3 a.

FIG. 4 c illustrates a further embodiment of the invention, where theapparatus comprises two light modulating arrangements 62, 63, e.g. ofthe type illustrated in FIG. 2.

The illustrated embodiment comprises two separate exposure heads 60, 61,each carrying a modulating arrangement 62, 63.

The illustrated embodiment of the invention has the advantage that theillumination, when applying a scanning e.g. in the direction of theillustrated arrows, may be optimized carefully to the illuminationsurface, thereby avoiding the above-described “over-scanning”. Inprinciple, any superfluous scanning may be avoided due to the fact thatthe scanning performed by the exposure heads 60, 61 may be adapted toavoid any conflicting movement between the applied exposure heads 60,61.

The illustrated embodiment, featuring a number of free-running exposureheads illuminating an illumination surface by scanning, is quiteadvantageous with respect to efficiency due to the fact that thescanning movement as such ensures a high-speed illumination, while thefree-running heads ensure that the illumination of the illumination areamay be optimized as described above.

Evidently, the embodiment of FIG. 4 c may be modified to incorporatefisher illumination heads, e.g. three or further heads in total.

1. Light illumination apparatus comprising: at least one exposure head;at least two light modulating arrangements, each of said two lightmodulating arrangements comprising a spatial light modulator and anassociated light emitter arranged for illumination of an illuminationsurface via said spatial light modulator; each of said two lightmodulating arrangements being digitally controlled; said apparatusfurther comprising means for performing a relative movement between saidat least one exposure head and said illumination surface in at least onedirection; wherein the exposure head is adapted for scanning in twotransverse opposite directions.
 2. Light illumination apparatusaccording to claim 1, wherein said at least two light modulatingarrangements are arranged on a single exposure head.
 3. Lightillumination apparatus according to claim 1, wherein said relativemovement is a scanning movement.
 4. Light illumination apparatusaccording to claim 1, wherein said relative movement is established bymoving the at least one exposure head relative to said illuminationsurface.
 5. Light illumination apparatus according to claim 1, whereinsaid relative movement is established by moving said illuminationsurface relative to the at least one exposure head.
 6. Lightillumination apparatus according to claim 1, wherein the at least oneexposure head comprises the two light modulating arrangements.
 7. Lightillumination apparatus according to claim 1, wherein said lightmodulating arrangements are arranged on at least two different exposureheads and where said exposure heads perform scanning movements over theillumination surface.
 8. Light illumination apparatus according to claim1, wherein said spatial light modulators are arranged so as toilluminate at least two substantially separate sub-areas of saidillumination surface.
 9. Light illumination apparatus according to claim1, wherein said spatial light modulating arrangements are aligned sothat rows of both light modulators are parallelly oriented.
 10. Lightillumination apparatus according to claim 1, wherein said spatial lightmodulating arrangements are aligned so that neighboring rows of the atleast two spatial light modulators are positioned substantially so thata distance between the neighboring rows of the at least two spatiallight modulators is substantially the same as a distance between rows ofthe individual light modulators.
 11. Light illumination apparatusaccording to claim 1, wherein an “x-projection” of a distance betweencenters of at least two of the spatial light modulators is less thanapproximately 200 millimeters.
 12. Light illumination apparatusaccording to claim 1, wherein a “y-projection” of a distance betweencenters of two of the spatial light modulators is less thanapproximately 50 millimeters.
 13. Light illumination apparatus accordingto claim 1, wherein a distance between centers of two of the spatiallight modulators is substantially 122.7 millimeters or 121.73millimeters when applying SXGA and XGA, respectively.
 14. Lightillumination apparatus according to claim 1, wherein said exposure headcomprises cooling means.
 15. Light illumination apparatus according toclaim 1, wherein each spatial light modulating arrangement comprisesindividual cooling means.
 16. Light illumination apparatus according toclaim 8, wherein said substantially separate sub-areas compriseneighboring surfaces of said illumination surface.
 17. Lightillumination apparatus according to claim 1, wherein said at least onedirection is substantially transverse to a relative movement of saidillumination surface.
 18. Light illumination apparatus according toclaim 1, wherein said at least one direction establishes that anilluminated pixel on said illumination surface is illuminated by meansof a least two light modulators of said spatial light modulator. 19.Light illumination apparatus according to claim 1, wherein said at leastone direction establishes that an illuminated pixel on said illuminationsurface is illuminated by means of at least one modulator row of saidspatial light modulator.
 20. Light illumination apparatus according toclaim 1, wherein said exposure head is movable in at least twodirections with respect to said illumination surface.
 21. Lightillumination apparatus according to claim 1, wherein said light emittercomprises a light source.
 22. Light illumination apparatus accordingclaim 1, wherein said light emitter comprises at least one lightemitting end of an optical guide coupled to a light source.
 23. Lightillumination apparatus according to claim 1, wherein said light emittercomprises a lamp.
 24. Light illumination apparatus according to claim 1,wherein said light emitter comprises an a LED matrix.
 25. Lightillumination apparatus according to claim 1, wherein said spatial lightmodulator comprises a DMD chip.
 26. Light illumination apparatusaccording to claim 1, wherein said spatial light modulator comprises amicro-mechanical transmissive light modulator.
 27. Light illuminationapparatus according to claim 1, wherein said illumination surfacecomprises a printing plate.
 28. Light illumination apparatus accordingto claim 1, wherein said illumination surface comprises a lightsensitive material.
 29. Light illumination apparatus according to claim1, wherein an x-direction between centers of the spatial lightmodulating arrangement is less than 150 mm.
 30. Light illuminationapparatus according to claim 29, wherein the x-direction between centersof the spatial light modulating arrangement is substantially.
 31. Methodof illuminating an illumination surface, whereby the illumination isperformed by a light illumination apparatus according to claim 1.